In this study of Safety and Efficacy of Doxycycline in Patients with Non-Ischemic Cardiomyopathy Population, we will enroll 24 patients with a clinical diagnosis of heart failure and non-ischemic cardiomyopathy (recent imaging study documenting LV ejection fraction <50%, and no history of coronary or ischemic heart disease) in a single-center, randomized, double-blinded, placebo-controlled clinical trial with allocation 1:1:1 to Doxycycline 100 mg twice daily or Doxycycline 20 mg twice daily or Placebo for 2 weeks.